Answer this question truthfully
### Question: What causes Transitional cell carcinoma?
### Response: In the United States, bladder cancers usually start from the cells lining the bladder (called transitional cells).
These tumors are classified based on the way they grow:
Papillary tumors have a wart-like appearance and are attached to a stalk. Nonpapillary (sessile) tumors are much less common. However, they are more invasive and have a worse outcome.